Experimental and Numerical Assessment of Residual Stresses in AA6061 After Surface Treatment by Deep Cold Rolling

Abstract

Deep cold rolling is a mechanical method of surface treatment used to adapt the desired surface properties in machine components for aerospace industries. In this process, localized plastic deformation is rendered on the surface by rolling a form tool wheel on the specimen to condense high dislocation density which imparts high compressive residual stresses resulting in increased tensile and fatigue strength. The main focus of the present study is to characterize the distribution of residual stresses on the surface and subsurface of an 8-mm-thick plate made of an aluminium alloy AA6061-O, after deep cold rolling operation to different depths of 0.5, 1, 1.5 and 2.0 mm. The observed residual stresses are correlated with the microstructural features in the deformed depths of the specimens. The residual stress and grain size in the deformed specimens are examined by using grazing incidence X-ray diffraction and electron backscatter diffraction technique, respectively. It is observed that deep cold rolling leads to significant grain refinement, resulting in high values of residual stresses through thickness. The compressive residual stresses are found to be higher on the surface of the specimen and reduce gradually with the penetration depth. The experimental results are compared with the results obtained by FE analysis using ABAQUS. A good agreement is observed between the experimental and the simulated values of residual stresses and the trends of stress distribution pattern.